It goes mouldy.
Then you throw it away.
This depends on temperature and humidity of your area. Left in the bread box wrapped in plastic about 3 to 5 days. Refrigerated about 7 to 10 days and frozen, several weeks.
Toasted bread does not spoil! it molds!
I find bread goes mouldy in about a week if left in its plastic bag - but that's in an English climate.
it takes 7 days if left out
Seven.
A bread box is a small, enclosed space. In the days before plastic bags and plastic wrap, that small space would become more humid from the bread in it and the enclosure would reduce the rate at which the humidity was diffused. Thus, the bread in the bread box would not dry out as quickly as it would if left on the cupboard shelf. Dried bread is stale bread and is not fresh.
Bread will get moldy whether bagged or not. If moist bread is contained in a plastic bag, the moisture would promote mold growth. Bread left open in a dry room would lose moisture, creating a dryer surface that would slow mold growth.
Around seven or eight days.
I have some left over bread.
There are seven days in a week so: 71 days / 7 days/week = 10 weeks and 1 day left over.
Since there are seven days per week, then simply divide the number of days by seven. Any remainder in your problem would be days left over, or a partial week. 165 / 7 = 23 weeks and 4 days
Banana bread can typically be left at room temperature for about 2 to 4 days before it starts to go bad. To maximize freshness, store it in an airtight container or wrap it tightly in plastic wrap. If you want to keep it longer, consider refrigerating it for up to a week or freezing it for several months. Always check for signs of mold or off smells before consuming.